1. Field
Aspects described herein relate generally to methods and apparatus for performing Fast Fourier Transforms (FFTs) and Inverse-FFTs (IFFTs). More particularly, aspects relate to performing FFTs and IFFTs with different resolution using one set of common hardware.
2. Background
FFTs and IFFTs are extensively used in the communication arts, especially in wireless communication. Aspects of embodiments disclosed herein are application in many types of communication systems in which the conditions for application can be found. Because aspects are to be described in connection with exemplary embodiments in the field of wireless communication under the IEEE 802.11n standard as published at the time this application is filed, incorporated herein by reference, some features of systems complaint with IEEE 802.11n are described.
Systems compliant with IEEE 802.11n have two channelization modes, a 20 MHz mode and a 40 MHz mode. These modes are provided in support of the Multiple Input, Multiple Output (MIMO) antenna architecture of the system. Conventionally, in order to create a stream of orthogonal data symbols, i.e., a stream of symbols distinguishable by a receiver, a 64-pt FFT and IFFT (one at the transmitter and one at the receiver) is used with a 20 MHz channelization rate. Conventionally, in order to support a 40 MHz channelization rate, twice the resolution would be needed, requiring use of a 128-pt FFT and IFFT.